I agree it's a terrible system.....for entirely different reasons.
Damage Resistance is entirely too strong. Anything above 80% reduction of damage is stupidly powerful, to the point where only the most negligent players who don't know how to look at their health bar will actually die. Combine this with an ability to pause time and insta-heal stimpacks (assuming that carries over from FO3 too), then where on earth is the challenge?
DT was a good system because damage remained high. Both for you, and for your opponent. That deathclaw's 250 damage will only be reduced to 200 and barely afford you a third hit you can survive, but you too will only see your 220 damage shot reduced to 205. Either of you can kill the other, the X-factor determining the factor being your aim. Compare this to FO3 where their 150 damage (was less in FO3, as NV offered stronger forms) became a pathetic 30 damage a hit. 30 damage...? I can survive ten hits of this [censored]....But oh no, they gotta make sure I'm also hitting him for 30 damage for a nice, tedious slugfest that does nothing but waste resources like ammo and stimpacks.
I also find the complaint that power armor didn't fully negate damage from 9mm pistols to be ridiculous. In a practical sense, do you honestly expect to die if that 9mm shot is hitting you for 2 damage? I could stick 20 people armed with 9mm pistols on you and you'd still win with ease. Power Armor in New Vegas functioned exactly as FO3's power armor when DT negated all damage: it let only 20% of the enemy's damage through, making you practically a god.
Several people have pointed out the best solution would be a mix of both stats, ideally with damage resistance not getting too high (keep it below 30%), then stick DR only on power armor or the higher grade medium armors. This ensures that Light armor doesn't outpace power armor in a practical sense while still not making light armor worthless, should you just provide it with perk benefits such as movement speed and crit.
But yeah, this is actually one of my biggest laments for FO4 and one of the biggest reasons I feel I won't be dying. Go review the footage we saw again, then go watch the Power armor vs. Deathclaw fight. The minigun is tickling the damned deathclaw, suggesting Bethesda hasn't learned a thing and once again makes their enemies "harder" by giving them more HP and defense rather than damage. Meanwhile, you can watch the player's HP bar and see that each Deathclaw hit does about 10% health damage, making it practically identical to the damage we saw in FO3. If this is a game where fights are exceedingly slow-paced and I can pause time to insta-heal myself to full, then I don't see myself enjoying it much, since I enjoy a decent challenge.
DT means a .50 caliber sniper shot still feels like a .50 caliber sniper shot, whereas 9mm begins to only tickle or annoy you.
DR means I can shoot you in the face with a mini nuke and somehow you're perfectly fine "becuz powur armurz."
Let's not kid ourselves about which system is more stupid when left alone.